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Human Tim8a, Tim8b and Tim13 are auxiliary assembly factors of mature Complex IV

ABSTRACT: Human Tim8a and Tim8b are paralogous intermembrane space proteins of the small TIM chaperone family. Yeast small TIMs function in the trafficking of proteins to the outer and inner mitochondrial membranes. This putative import function for hTim8a and hTim8b has been challenged in human models, but their true molecular function in cells has not been defined. Likewise, why human cells possess two Tim8 proteins and any potential redundancy is not clear. We demonstrate that hTim8a and hTim8b function in the assembly of cytochrome c oxidase (Complex IV). Using affinity enrichment mass spectrometry, we catalogue the interaction network of hTim8a, hTim8b and hTim13, identifying subunits and assembly factors of the Complex IV COX2 module. hTim8-deficient cells have a COX2/COX3 module defect, albeit less severe than a COX17KO cell line, and exhibit an accumulation of the S2 subcomplex. This suggests that hTim8a and hTim8b are required for assembly of Complex IV via interactions with intermembrane-space exposed subunits. We propose hTim8-hTim13 complexes act as chaperones to stabilise the intermediate S3 subcomplex, promoting assembly of monomeric Complex IV.

INSTRUMENT(S): Orbitrap Eclipse, Orbitrap Fusion Lumos, Q Exactive

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Cell Culture

SUBMITTER: Alex Anderson

LAB HEAD: Diana Stojanovski

PROVIDER: PXD037906 | Pride | 2023-05-10

REPOSITORIES: Pride

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